Automatic telephone systems



June 25, 1957 Filed April 29, 1954 H. L. HORWITZ ET AL AUTOMATICTELEPHONE SYSTEMS 5 Sheets-Sheet 1 ATTORNEY June 25, 1957 H. L. HORWITZET AL 2,797,262

AUTOMATIC TELEPHONE SYSTEMS Filed April 29.. 1954 June 25, 1957 H.HORWlTZ ETAL AUTOMATIC TELEPHONE SYSTEMS Filed April 29. 1954 5 sheetssheet 3 INVENTOR ATTORNEY Jime 25, 1957 H. L. HORWITZ ET AL 2,797,262

AUTOMATIC TELEPHONE SYSTEMS 5 Sheets-Sheet 4 Filed April 29, 1954 /o.MVU vmum 0 NW? r w TIIIL Q m Ills m l. w s H k T @i W Hill Milllb N TILOIL INVENTOR 19.1.. HO/PW/TZ 6 L. #145557? BY ATTORNEY 7 2,797,262Patented June 25, 1957 ice AUTQMATIC TELEPHQNE SYSTEMS Henry LeopoldHorwitz, Nntlcy, and George Louis Hasser, Paekanaclr Lake, N. 5.,assignnrs to lntcr-= national Telephone and Telegraph (Importation, NewYork, N. Y., a corporation of Maryland Application April 29, 1954,Serial No. 426,516 11 Claims. (Cl. 17927) This invention relates toautomatic telephone systems and more particularly to multi-office areasystems in which toll calls are extended via a tandem oifice to atributory or terminating office over trunks used for both extended areaand toll service.

One object of the invention is to prevent local subscribers in thetandem office from using the toll features of the tributory ofiice.According to one feature of the invention this is accomplished bysending a supervisory signal to the repeater in the tandem oflice,during the interdigital time of the number dialled, by a switch assignedonly for toll service (for example, for setting up verification calls)for the purpose of preventing further dialing if the call is originatedby a local subscriber in the tandem olfice.

According to a further feature of the invention the repeater in thetandem ofiice is arranged to distinguish by means of a forward call iseither originated locally or from the toll board, and the repeater isarranged to prevent further dialing as soon as the answer supervisorysignal is received when the call is originated by a local subscriber inthe tandem oflice.

According to another feature of the invention, when the trunk lines fromthe tandem oflice to the tributory oifice are used for both extendedarea and toll service, this repeater extends answer supervisory signalsimmediately but introduces a delay in response to the signal itself topermit further dialing if the call is originated from a toll board. Thisrepeater has two paths of access, and on outgoing toll calls, dependentupon the path of access over which it is taken into use, it is arrangedto send automatically a single impulse in order to permit a subscriberin the tributory ofiice to reach the toil board via the equipment in thetandem oiiice by dialing a single digit.

According to a still further feature of the invention the auto-to-manualrepeater which is utilized at the tandem ofiice to receive calls fromand extend calls to the toll board has two points of access for outgoingcalls, one providing answer supervision for calls originated locally inthe tandem ofiice, and the other arranged to pass answer supervision forcalls originated in the tributory ofiice.

These and other features of the invention pointed out in the appendedclaims will be understood from a consideration of the following detaileddescription of one embodiment of the invention taken in conjunction withthe accompanying drawings.

In the accompanying drawings Fig. 1 is a circuit diagram of the two-wayauto-to-auto repeater at the tributory or terminating ofiice;

Fig. 2 is a circuit diagram of the two-way auto-to-auto repeater at thetandem office;

Fig. 3 is a circuit diagram of the two-way auto-tomanual repeater at thetandem oflice;

ground on the private wire that the Fig. 4 is a circuit diagram of averification distributor; and

Fig. 5 is a layout diagram of a multi-office system showing theinterconnection of the repeaters and of the associated switchingequipment.

In the drawings, as is common in present day automatic telephoneswitching practice, the relay contacts are shown divorced from theirassociated relay coils. In order to simplify the reading of thesecircuits, the relays and their associated contacts are givencorresponding reference letters. For example, the relay F, in Fig. 1, isgiven the reference which indicates that this relay have five contactsets which are respectively indicated F1, F2, F3, F4 and F5 on thedrawing.

Calls from Tributory Ofiice to Tandem Office (local and toll) When acalling party of the Tributory Oflice removes his handset and dials thenumber of a wanted subscriber in the Tandem Ofiice, or the digit 0 tocall the toll operator, the call is extended in known manner over thestation line circuit LC, Fig. 5, line finder LF, 1st group selector GSto an idle two-way repeater Repl giving access to a trunk Trul extendingbetween the Tributory Ofiice and the Tandem Ofiice.

Call to subscriber in Tandem Ofiice (normal access) When the repeaterRepll is seized by a subscriber making a call to a wanted party in theTandem Office over the path of normal access +L(1), L(l), P, Fig. 1,absence of ground on the P lead allows the preceding equipment to seizethis circuit and switch through the subscribers loop, closing thecircuit to relay A over the +L(1) and L(1) leads and through thewindings of repeating coil RC. A operates and, in turn operates relay Fover contacts A2. F at contacts F1 removes the 600 ohm termination YFfrom the line and at contacts F4- operates relay B. B at contacts B1removes ground from the lead ATE in order to meter an all trunk busycondition if all such other grounds have been removed in otherrepeaters, and closes a circuit to operate slow operating relay M viaits 3-4 winding, at contacts B3 places ground on the P lead in order tomake this circuit busy to other outgoing calls and to hold the precedingequipment, and at contacts B5 prepares a circuit to relay C. Beforerelay M can operate, relay D operates over the contacts B1 and B4 ofrelay B and short circuits the operating winding of relay R. Thecontacts of relay M have no effect at this time other than releasingrelay D at contacts M4.

Since the circuit is arranged for simplex dialing over the trunk, relayA at contacts A1 applies resistance bate tery over lamp BRA, the windingof relay G and conductor DL to the and leads of the trunk, thus causingthe succeeding equipment in the distant oflice to be seized. Relay Goperates. Relay H is slow to operate and does not operate should acircuit be closed from ground to H during the operation of relays G andF.

In the Tandem Office, resistance battery on the and leads of the trunkenergizes the relay G of the. repeater, Fig. 2. The trunk enters Fig. 2on the left-hand side and the circuit for G extends over conductor DLWinding of G contacts K 5, A 1, and rectifier MRA 3 to ground. Relay Goperates, at contacts G 2 completes part of the loop for and at contacts6% closes a circuit for relayD Relay D atcontacts D 1 removes groundfrom the all trunks dition, at..D 2 grounds the P lead to make thisseizing the succeeding equipment,

3' busy to outgoing calls, at D 3 prepares a circuit for relay C and atD 4 closes a circuit over H 1, F 3 for upper winding 1-2 of relay Swhich locks over its contacts S 4 and completes the loop for seizing anincoming selector 152 (see Fig. This loop extends from the lead SW, Fig.2, contacts E 1, G 2, S 5, winding 7-8 of repeating coil RC contacts S3, rectifier MRA I, winding 3-4 of coil RC contacts S 9 to the lead +SW.

Relay A, Fig. 1 follows each series of dial pulses received. When atnormal, A at contacts A2 opens the circuit to relay F and closes thecircuit to relay C. C operates on the first impulses of each series.Relays B and C are slow to release and remain operated during impulsing.Relay C at contacts C1 opens the circuit to relay H to prevent itsoperation during pulsing, at contacts C2 shuns winding 34 of repeater RCwith resistor YE and also shunts at contacts C3 the winding of G withresistor YD in order to prevent impulse distortion, and at contacts C2opens the circuit to the terminating resistor YF to prevent it frombeing reapplied to the line should relay F restore during pulsing.

When relay A is at normal, it also removes at contacts A1 resistancebattery from the DL lead and from the and wires of the trunk therebypulsing over the trunk. a

After the last pulse of each series, relay A remains operated, openingthe circuitto relay C, and reclosing the circuit to relay F. Relay Crestores.

In the tandem ofiice, relay G Fig. 2, follows the impulses received, andin its normal position opens at G 2 the loop to the incoming selector.Relay C operates over G 1, D 3 and R 6 on the first impulse of eachseries, and at C 2 shunts the winding 34 of repeating coil RC withresistor YE to improve impulsing conditions.

After the last impulse of each series, relay G remains operated,recloses the loop circuit to the succeeding equipment, releases C andrecloses the circuit to relay D Relays C and D are slow to release andremain operated during impulsing.

The succeeding local equipment follows the impulses received from Gestablishes a connection to the dialed line, and signals the dialedline, all in well-known manner.

In the repeater of Fig. 2, when a succeeding switch reverses batteryover the +SW and -SW leads on the reply of the wanted subscriber relay Foperates over its 12. winding in series with rectifier MRA Z. Relay F atcontacts F 3 operates relay A over its 3-4 winding, operates relay B atcontacts F 4 and shunts contact G 2 at F 5 to hold the succeedingequipment operated when relay G restores.

Relay A at contacts A 1 replaces ground with resistance battery overresistor YA and lamp BRA to winding of G and conductor DL thus giving ananswer supervisory signal to repeater Repl. Relay G releases, opens thecircuit to D and operates H over contacts G 1, F 2, C 1, M 1 and H 5.Relay H locks to ground over H 5, MRA 4 and B 1 and operates relay Rover K 2, H 4, F 2, G 1. Relay R closes an additional circuit to relay Bplaces an additional short on the pulsing contact of G at R 3, closes atR 7 a circuit to relay E from the PSW lead and at R 6 opens the circuitto relay C Relay D is slow to release and does not restore until relay Ehas operated.

Relay E operates from ground returned over the PSW lead, atE 2 bridgesthe contact R 7 to maintain a circuit to its winding, closes at E 3 aholding circuit to relay S via its 34 winding, opens at E 1 a short onthe contact R 3 in the transmission circuit in preparation for therelease and closes at E 4 a holding ground to the 34 winding of relay PIn the Tributory exchange, the replacing of ground on the and leads ofthe trunk with resistance battery causes the relay G, Fig. l to restoreand relay H is energized over contacts G1. Relay H at contacts H5 locksto ground on the P wire and opens its operating circuit,

at contacts H1 opens the circuit to relay C, and at contacts H4 operatesrelay S. Relay S at contacts S4 closes an additional holding circuit torelay B and at contacts S5, S9 reverses battery towards the calling lineto give an answer supervisory signal.

When the calling party disconnects first, the circuit to relay A, Fig.1, is opened. Relay A restores and releases relay F.

The release of A replaces resistance battery with ground on the DL wireand and leads of the trunk (simplex) over the winding of relay G, thusgiving distant disconnect supervision and reoperating relay G. Relay Fopens the circuit to relay S but recloses an alternate circuit to S overcontacts M3, G1, B2, F2, C1 and H4. Relay S maintains relay B operated.If relay S releases momentarily during the transfer time of its holdingcircuit, relay B remains operated since it is slow to release.

In the repeater, Fig. 2, at the Tandem Ofiice, relay G operates and atcontacts G 1 opens the circuit of relay R which at contacts R 3 opensthe loop to the succeeding equipment and transfers the holding circuitof relay B to contacts F 4. When ground is removed from the PSW lead,relays E S and F release. A circuit is now closed over contacts S 6, A2, B 5, R 6 for relay C which operates relay M over C 4. At contacts M 2relay M grounds the P lead to hold the circuit busy. The release ofrelay F opens the circuit of relay B which at B 5 opens the circuit ofrelay C which in turn at C 4 releases relay M Relay M now removes groundfrom the P lead rendering the circuit idle for succeeding calls.

When the repeater Repl is seized by a subscriber switch in known mannerreverses battery over the -SW and +SW leads, release relay F Fig. 2.Relay F opens at P 3 the circuit of relay A which in turn at contacts A1 connects ground via winding of relay G to the DL lead. Relay Genergizes and holds relay R over G 1.

In Fig. 1 when the resistance battery over the DL lead is replaced byground, relay G operates and releases S as before.

Relay S at contacts S5 and S9 reverses battery to the calling party inorder to give disconnect supervision.

When the calling party disconnects, relay A is released and, in turn,releases relay F.

7 Relay A replaces resistance battery with resistance ground on theconductor DL and the and leads of the trunk (simplex) over the windingof G, thus allowing the succeeding equipment to release and releasing G.Relays B, H and M restore. Ground is removed from the P lead, allowingthe preceding switches to restore, and this circuit is ready for thenext call.

In the repeater, Fig. 2, at the Tandem Ofiice, when the DL lead isgrounded at the Tributory Ofiice, relay G releases and opens the circuitto relay R Relay F operates and relay R restores and opens the loop tothe succeeding equipment. When ground is removed from the PSW lead, therelays E S and F restore and the circuit of Fig. 2 is released asalready described.

Call to toll operator (pulse sending access) When the repeater Repl isseized by a subscriber making a call to the toll operator via the TandemOffice, over the alternative path of access (10th level of selector GS,Fig. 5) comprising the leads +L(2), -L(2), and P, Fig. l, relays A, F,B, M and D operate as before.

Relay D at contacts D6 places a multiple short circuit across the 12winding of relay R which is connected in series with the L(2) lead. Theremaining contacts of D are not effective at this time. Relay Moperates, at contacts M1 opens part of the circuit to the DL lead, atcontacts M2 opens one of two shorts across the 1-2 winding of relay R,at contacts M5 grounds the P lead to short circuit the 1-4 winding ofthe tone coil TC, at contacts M4 short circuits its 12 winding and opensmenace '5 the circuit to relay D. Relay D releases slowly, due to coppersleeve on its core, to provide time for the distant equipment to beseized. Relay D, on release, at contacts D6 removes the remaining shortacross the 12 winding of relay R. Relay R now operates in series withrelay A over the calling subscribers loop. Relay R closes a circuit toits 3-4 winding at -a preliminary make contact R5. When the 3-4 windingof R is energized, the relay operates all its contacts. Relay R nowopens at contact R1 the circuit to relay M, at contacts R2 opens theloop to the normal access, at contacts R3 short circuits the 55 contactto prevent its eifect on answer, at contacts R4 opens the circuit to its1- 2 winding without opening the loop, at contacts R6 removes groundfrom the circuit controlling the operation of relay H and connectsground to the ring start lead 'RST to start or continue the operation ofthe ringing equipment, and rat contacts R7 opens the battery connectionto the DL lead to start a dial pulse. The relay M is designed to releasein a time equivalent to a dial pulse. This time may 'be adjusted bychanging the value of the shunt resistance YS. When relay M releases,the battery connection to the DL lead is restored at contacts M1 and theequipment in the distant oflice has thus received a single insertedpulse. Relay M also at contacts M3 connects ground to the contact G1controlling the answer supervisory circuit, replaces at contacts M2 themultiple short across the 12 winding of relay R, at contacts M4 removesthe short from across its own l2 winding, and at contacts M removes theshort from across the l4 winding of the tone coil TC to prepare fortransmitting pay station tone to an operator on answer.

The circuit now waits answer by the called party.

Ground on the DL lead over the winding of relay G caused the seizure ofthe repeater, Fig. 2, at the Tandem Oflice, as described in connectionwith seizure over the normal path of access. Relay G responds to theadditional inserted impulse and the incoming selector 182, Fig. 5, isstepped to its first level in which it hunts for 'an idle auto-to-manualrepeater Rep3, the circuit of which is shown in detail in Fig. 3.

Absence of ground on the P lead allows the incoming selector to switchthrough, closing the circuit to relay A over the +L( 2) and L(2) leadsthrough line loop and through the windings of the repeating coil RCRelay A now operates, at contacts A 1 removes ground through the windingof relay G from the DL lead, at A 4 connects a multiple ground to its1-2 winding, and at A 2 and A 3 closes the circuits to relay M and BRelay B operates, at B 1 removes a ground from the lead ATB to providefor metering an all trunks busy condition and closes the circuit to the3-4 winding of relay C and places ground on the ring start lead RST inorder to start or continue the operation of the associated ringingequipment, at B 2 opens part of a circuit to relay D to prevent itsoperation on an outgoing call and closes part of an alternate circuit torelay M at B 3 applies resistance battery over the winding of relay G tothe DL lead, thus causing the operator in the distant ofiice to besignalled, at B 4 places ground on the P lead through the I4 winding ofthe TC tone coil in order to make this circuit busy to other outgoingcalls and to hold the preceding equipment operated, and at B 5 closesthe circuit to relay K in parallel with condenser QA and resistance Gthus allowing condenser QA to become charged. Relay G operates, at G 1opens the circuit to relay M and closes part of the alternate circuit toM Relay M is slow to operate and does not operate during the operatetime of relay G Relay K operates and at K 1 connects ringback tone overlead RBT to the L(2) lead through condenser QD to advise the dialingparty that the operator is being signalled. Relay C operates, at C 2prepares the peg count circuit PC, and at C 1 removes the 600 ohmtermination YD from the line.

When the call is answered by the operator, ground is post pay stationtone over the Plead and Winding 23 of coil TC through condenser QG tothe operator, at M 2 opens the circuit to relay K and closes a lockingcircuit to relay B at M 4 removes ground from the RST lead to allow theassociated ringback equipment to restore,

at M 5 removes a multiple ground from the 12 Winding of relay A and at M3 and M 7 reverses the polarity of the calling line via the +L(2) andL(2) leads, to provide answer supervision to the preceding equipment aspreviously described in connection with a call com pleted over normalaccess. This signal is necessary only when the call to this repeater hasbeen originated over a trunk from another olfice. When the circuit torelay K is opened, condenser QA discharges through resistance YG and thewinding of relay K thus delaying the release of relay K Relay K uponrestoring, at K 1 opens the circuit for furnishing the operator with asplash of post pay station tone if the call originated from a paystation. Tone coil TC is of sufficient impedance to prevent shunting thepost pay station tone current to ground.

In the repeater of Fig. 2 when a succeeding switch reverses battery overthe SW and +SW leads when the call is answered, relay F operates overits 1-2 winding in series with rectifier MPeA 2. Relay F at contacts F 3operates relay A over its 34 winding, operates at contacts F 4 relay Band shunts contacts G 2 at P 5 to hold the succeeding equipment operatedwhen relay G restores.

Relay A replaces ground with resistance battery over resistor YA andlamp BRA to the winding of relay G thus giving answer supervision to thedistant party. Relay G releases, opens the circuit to relay D andoperates relay 1-1 over G 1, F 2, C 1, M 1 and H 5. Relay H locks toground over H 5, MRA 4 and B 1 and operates relay R over K 2, H 4, F 2,G 1. Relay R closes an additional circuit to B places an additionalshort on the pulsing contact or" G 2 of relay G at R 3, closes at R 7 acircuit to relay E from the P sw lead and opens the circuit to relay CRelay D is slow to release and does not restore until relay E isoperated.

Relay E operates from ground returned over the P sw lead, at E 2 bridgesthe contact R 7 to maintain a circuit to its winding, closes at E 3 aholding circuit to relay S via its 34 winding, opens at E 1 a short onthe R 3 contact in the transmission circuit in preparation for therelease and closes at E4 a holding ground to the '34 winding of relay FWhen the succeeding equipment replaces ground on the DL lead withresistance battery, relay G, Fig. 1, restores. Relay G closes a circuitfor relay H at contacts G1.

Relay H at contacts H5 locks to ground on the P wire and opens itsoperate circuit, at contacts H1 opens the circuit to relay C, and atcontacts H4 operates relay S. Relay S at contacts S4 closes anadditional holding circuit to relay B, closes at contacts S7 a circuitfor the transmission of paystation tone received via the P lead and the2-3 winding of the tone coil TC and extended via a make contact J1 ofrelay I and condenser QF to the L(2) lead. This tone is connected to theP lead only on paystation lines and is utilized to inform the operatorthat the call is originated on a paystation. Relay S at contacts S1opens the circuit to relay I which was energized in parallel with relayM by a make contact B1 of B, and at contacts S2 opens the ground to theRST lead. Relay J is paralleled by a 1000 ohm resistor YM and a 40 MFcondenser QE which discharges through the winding of relay I when itsenergizing circuit is opened by relay S. Relay 1, therefore, is madeslow-to-release thus providing a time interval in which the paystationtone is transmitted to the operator. 7 p

The paystation tone is not transmitted when the call is originated viathe normal access as relay R is not operated and hence relay M remainsoperated. Relay M when operated short circuits the tone forwarded overthe P lead by grounding terminal 1 of the tone coil TC at contacts M5.

Answer supervision is not returned on' a connection via the pulsesending access.

Transmitter battery is supplied to the calling party through thewindings of relay A. The windings of repeat coil RC and condenser QDcomplete the transmission circuit.

When the calling party disconnects first, the circuit to relay A, Fig.l, is opened. vA restores and releases relay F. V

The release of A replaces resistance battery with ground on the DL Wireand and leads of the trunk (simplex) over the winding of relay G, thusgiving distant disconnect supervision and reoperating relay G. Relay Fopens the original circuit to relay S but recloses an alternate circuitover contacts M3, G1, B2, F2, C1 and H4 which maintains relay Boperated. If relay S releases momentarily during the transfer time ofits holding circuit, relay B remains operated since it is slow torelease.

When resistance battery is replaced by ground on DL relay G operates andopens the circuit to relay R which opens the loop to the succeedingequipment and transfers the holding circuit for relay B to a groundcontrolled by relay F Since the connection is to a toll operator, theground returned on the PSW lead will maintain the connection, andrelease Will not take place until the toll operator disconnects.

When the loop to the repeater, Fig. 3 is opened, relay A restores. Theconnection is held, however, by ground on the P lead over B 4 andwinding 14 of TC.

Relay A upon restoring, at A 1 replaces resistance battery on the DLlead through the winding of relay G with ground, thus closing thecircuit to relay G and giving the operator in the distant oflicedisconnect supervision. Relay A also opens at A 2 the circuit to relayM3 and prepares an alternate circuit M and at A 3 opens a multiplecircuit to relay B Relay G operates, closes at G 1 the alternate circuitto M and connects ground via the contacts L 5, G 2 and L 4 to the 12winding of A to provide for the reoperation of relay A if the operatordoes not disconnect and the subscriber recloses the loop. Relay M isinherently slow to release and remains operated for the operate time ofrelay G and transfer time of relay A When the operator in the distantoffice disconnects, resistance battery on the DL lead is replaced byground, thus opening the circuit to relay G Relay G restores and opensthe circuits to relays M and A Relay B restores and at B 4 removesground from the P lead to allow the preceding equipment to restore andremove ground from the PSW lead. When ground is removed from the P SWlead, relays E S and F release. When relays S and F release, a circuitis closed to relay C which, in turn, operates relay M Relay M groundsthe P lead to maintain the circuit. When relay B restores due to relay Freleasing it opens the circuit to relay C which releases and, in turn,releases relay M Relay M restores and at M 2 removes ground from the Plead thus making the circuit idle for succeeding calls. i

In therrepeater of Fig. l, relay G releases and in turn releases relaysB, H and R. Ground is removed from the P lead, allowing the precedingswitches to release and freeing the repeater of Fig. 1.

If the operator disconnects first, resistance battery on the DL- lead isreplaced by ground, thus :closing the circuit to' relay G which opensthe circuit of relay M The P lead is heldgrou'nded at contacts B 4,however, and holds the preceding equipment. Relay M reverses the batteryover the leads +L2, L2, and upon battery reversal over leads I-SW, SW,relays F A Fig. 2, release and ground is placed to winding of relay Gwhich operates together with relay G of Fig. When the calling partyhangs up, relays A, P, Fig. -1, release. In Fig. 1, when the resistancebattery over the DL lead is replaced by ground, relay G operates andreleases relay S, as before.

Relay S reverses battery to the calling party in order to givedisconnect supervision.

When the calling party disconnects, relay A is released and, in turn,releases relay F.

Relay A replaces resistance battery with resistance ground on the DLlead and the and leads of the trunk (simplex) over the winding of relayG, thus allowing the succeeding equipment to release and releasing relayG. Relays B, H and M restore. Ground is removed from the P lead,allowing the preceding switches to restore, and this circuit is readyfor the-next call.

In the repeater of Fig. 2 relay G releases and opens the circuit torelay R ,Relay R restores, opens the loop to the succeeding equipmentand transfers the holding ground for relay B to make a contact F 4 of FRelay F operates and closes the holding :circuit to relay B Relay R Fig.2, opens the loop to relay A Fig. 3, which grounds the winding of Gfreeing the repeater of Fig. 3 as already described. When ground isremoved from the P lead, the incoming selector restores and removesground from the PSW lead thereby freeing the repeater of Fig. 2.

Call from subscriber in Tandem Office to subscriber in Tributary OfiiceThe connection is extended in well-known manner from the subscriber linecircuit LC2, Fig. 5, over line finder LFl and group selector GSZ (fifthlevel) to an idle repeater Rep2.

Referring to the circuit of repeater Rep2 shown in detail in Fig. 2,absence of ground on the P lead allows the preceding equipment to seizethis circuit and switch through the calling loop, closing the circuit ofrelay A over the }L and L leads and through the windings of repeatingcoil RC Relay A operates and in turn operates relay F over its winding3, 4 and contacts A 2. Relay F removes the 600 ohm termination YF fromthe line at contacts F 1, closes a circuit via G 1, F 2, C 1, M 1, H 5to relay H connects at F 3 a multiple ground to the 1--2 winding ofrelay A and operates relay B via F 4, R 2. Relay B removes ground fromthe all trunks busy metering circuit ATB at B 1 and prepares the lockingcircuits for relays H and K at B 2 opens the circuit to relay D toprevent its operation on an outgoing call and prepares an alternatecircuit to relay H at B 3 grounds the P lead, at B 4 prepares a shortcircuit for relay G during dialing, and at B 5 prepares a circuit torelay C Relay A at A 1 applies resistance battery over the winding ofrelay G to the DL2 lead and the and leads of the trunk (simplex), thuscausing the succeeding equipment in the distant Tributory Ofiice to beseized. Relay G operates. Relay H is slow to operate and does notoperate should a circuit be closed from ground at G 1 during theoperation of relays G and F In the Tributory Office repeater Repl, Fig.l, relay G operates, closing a circuit to relay D. Relay D at contactsD1 opens a circuit utilized on outgoing calls to shunt the impedance ofthe relay G, at D2 opens a short across the thermistor TH to provide aslow operate time for the relay H, places at contacts D3 ground on the PSW lead in order to provide a ground marking for succeeding equipmentwhen required, closes at D4 a circuit to relay U, grounds at D5 the Plead to make this circuit busy to outgoing calls and at D6 shortcircuits the 12 winding of relay R. Relay U locks over U7, completes atUS, U10 and U11 a loop via the relay F from the +SW and SW leads toseize thesucceeding equipment, prepares at U a circuit to relay A, opensat U9 the termination across the and leads and connects a sparkquenching circuit comprising condenser QB and resistor YF across theimpulsing contact L1, at U6 prepares a locking circuit to relay D,prepares a circuit to the impulse correcting relays, at U4 shunts thecontact C1 in preparation for answer supervision, at contact U2 opensthe connection to the ATE lead and at U1 removes ground from the circuitcontrolling the locking of relay F.

Relay F does not operate at this time due to the polarity of the loopand the shunting effect of rectifier MRAl. The circuit is now ready toreceive dial impulses.

Referring to Fig. 2, relay A follows each series of dial pulsesreceived. When at normal, relay A opens at A 2 the circuit to relay Fand closes the circuit to relay C Relay C operates on the first impulseof each series. Relays B and C are slow to release and remain operatedduring impulsing. Relay C opens at C 1 the circuit to relay H to preventits operation during pulsing, shunts at C 2 winding 3-4 of repeatingcoil RC with resistor YE and at C 3 shunts the winding of relay G withresistor YD in order to prevent impulse distortion, opens also at C 2the circuit to the terminating resistor YF to prevent it being reappliedto the line should relay F restore during pulsing, and closes at C 4 acircuit to relay M Relay M operates to prepare at M 1 a circuit to relayR for reception of a preliminary answer supervisory signal undercircumstances which will be referred to later.

When relay A is at normal, it removes at contacts A 1 resistance batteryfrom the DLZ lead and from the and wires of the trunk.

After the last pulse of each series, relay A remains operated, openingthe circuit to relay C and reclosing the circuit to relay F Relay Crestores.

Referring now to Fig. l, the removal of battery from the DL leaddeenergizes relay G and when G closes its break contact G on release, itenergizes relay L via its 34 winding and a break contact T of relay T.Relay L operates, at L4 closes a circuit to the 34 winding of relay Tand closes a locking circuit to its 3-4 winding via MRA4 to hold onshort pulses, at L2 closes a holding circuit to relay D to prevent itsrelease on a long pulse, at L3 short circuits its primary winding toprovide a delay in its release and at Ll opens the loop to the incomingselector ISl (see Fig. 5). Relay T operates slowly to provide pulsetime, at T2 opens the circuit to relay L, at T1 opens a short on itsprimary winding to provide the relay with a faster release time, at T3closes a circuit to relay C, and at T2 locks to the pulse delivered byrelay G to prevent sending more than one impulse for a long impulsereceived.

Relay C operates, at C2 connects a 100 ohm resistor YE across onewinding 3-4 of the repeating coil RC to shunt its impedance to improvethe impulsing to the succeeding equipment and at C4 short circuits at250 ohm resistor YL in the shunt on the 1-2 Winding of relay T toincrease its operate time for succeeding pulses.

Relay L releases slowly due to the short on its 12' winding after relayT opened the circuit to its 3-4 winding. Relay L, on release, closes atLl the loop to the succeeding equipment, opens the original energizingcircuit to relay T, opens the holding circuit to relay D and opens theshort on its 1-2 winding. Relay T releases at this time or holds to theimpulse if it is still present. When relay G operates at the end of theimpulses, the circuit to relay T is opened. Relay T, on release,prepares a circuit to relay L from the impulsing circuit, short circuitsits 12 winding and opens the circuit to relay C. Relay C is slow torelease and remains operated throughout the digit.

Relay L reoperates on the next impulse and the cycle describedpreviously is repeated with the exception that 10 relay C is operated.After the last impulse of each series, relay G remains operated, holdingthe circuit to relays L and T open and D operated. Relay L in itsreleased condition holds the loop to the succeeding equipment closed.

When the call 'is answered, a succeeding switch reverses battery overthe SW and l-SW leads, allowing relay F to operate over its 1-2 Windingin series with rectifier MRA2. Relay F at F3 operates relay A over its3-4 winding, at P4 operates relay B and at P5 shunts contacts L1 to holdthe succeeding equipment operated when relay G (which pulses relay L)restores. Relay A at A1 replaces ground with resistance battery to thewinding of relay G. RelayG releases, opens at G1 the circuit to relay D,and operates relay H. Relay H locks over H5 to ground on the P wire,opens at H2 the circuit to the impulse correcting relays, and at H4operates relay S. Relay S closes at S4 an additional circuit to relay B,at SS places an additional short on the pulsing contacts L1 of relay Land at S3 recloses the circuit to relay D. Relay Dis slow to release andhas a holding circuit via H3 to prevent its release during the longoperate time of relay H. The spark suppressor SQA protects contacts P3of relay F.

The windings of repeat coil RC and condenser QD complete thetransmission circuit.

In the repeater, in Fig. 2, in the Tandem Office, when ground on the DLZlead is replaced with resistance -battery, relay G restores. Relay Goperates relay H over G 1, F 2, C 1, M 1.

Relay H locks to ground B 1 provided by B at H 1 opens part of theenergizing circuit of relay S operates relay R at H 4, and at H 2 and H3 prepares circuits to contacts of relay R to provide for the reversebattery supervisory signal. Relay R opens at R 2 a holding circuit torelay B opens at R 6 part of a circuit to relay C and at R 4 and R 8reverses battery to the calling party in order to give answersupervision. Relay R also at R 1 removes a short circuit from winding1-2 of relay K which operates over the P wire. Relay K locks to B 1 overits Winding 34 at K 3 places relay R under control of relay F atcontacts F 4, and at K 5 disables contact A 1 in the circuit of relay GTransmitter battery is supplied to the calling party through thewindings of relay A The windings of repeat coil RC and condenser QDcomplete the transmission circuit.

When the calling party disconnects first, the circuit to relay A isopened. Relay A restores and at A 2 released relay F The contact A 1 isnot effective due to the operation of relay K Relay F opens at F 4 thecircuit of relay R at P 3 removes ground from the 1-2 Winding of relay Aand at P 1 reconnects the termination of the and leads. Relay Rrestores, at R 4 and R 8 removes the answer supervisory signal, at R 5reconnects ground to the 1-2 winding of relay A after the line reversalis completed, at R 6 recloses part of a circuit of relay C and at R 2opens the circuit to relay B Relay B releases, at B 1 opens the circuitto relays K and H at B 3 removes a multiple ground from the P lead, at B2 prepares a circuit to relay D at B 4 opens part of a short circuitacross the relay G and at R 6 opens the circuit to relay C Relay Kreleases and at K 5 connects ground via A 1 to the DL lead via thewinding of relay G to provide disconnect supervision to the distantoffice. Relay G operates and closes the circuit to relay D Relay Doperates, connects at D 2 ground to the "P lead to maintain the circuitbusy and closes at D 1 a circuit to hold relay H which has not releaseddue to its slow release characteristics. H holds the circuit to relay Sopen at H 1 to prevent'its operation and the seizure of the incomingselector.

In the repeater, Fig. 1, at the Tributory Oifice, when resistancebattery on the DL lead is replaced with ground,

relay G operates. Relay G releases relay S." Relay S releases relay Dwhich, in turn, releases relay U and relay A. Relay U opens the loop tothe succeeding equipment. Relay F restores and, in turn, relays -B and Hrelease. Relay A replaces resistance battery with ground to the windingof relay G, thus releasing relay G. This circuit is then ready for thenext call. y

In the repeater, Fig. 2, relay G releases opening the circuit to relay DRelay D restores and releases relay H Relay C now operates and energizesrelay M which in turn maintains the repeater busy at contacts M 2. RelayC restores when relay D releases and opens the circuit to relay M whichremoves the ground from the P lead. The repeater is now idle and readyfor a new call.

Referring to the repeater, Fig. 1, at the Tributory Office, when thecalled party disconnects first, battery reversal over the -SW and +SWleads, causes relay F to restore.

Relay =F opens the circuit to relay S and a multiple circuit to relay B,prepares an alternate circuit to relay S, and releases relay A. Relay Areplaces resistance battery with ground to the winding of relay G, thussending a disconnect supervisory signal towards the calling line. RelayG operates and recloses the circuit to relay S. If relay S shouldmomentarily release during the transfer of its holding circuit, relay Bwill remain operated since it is slow to release. When the calling partyreleases, the preceding equipment replaces resistance battery withground on the DL lead. Relay G releases and, in turn, relays S, B, D, Uand H are released. Ground is removed from the P lead and this circuitis ready for the next call.

Referring to Fig. 2, when resistance battery is replaced by ground overthe -DL lead, relay G operates. No further action takes place until thecalling subscriber releases.

When the calling subscriber releases, relay A restores opening thecircuit to relay F Relay F releases, reconnects the termination to theand leads, opens the circuit to relay R removes ground from the 1-2winding of relay A and closes part of a circuit to relay S Relay Rreleases, opens the circuit to relay B reverses the polarity of theline, reconnects ground to the 1-2 winding of relay A and closes acircuit to relay C Relay C closes a circuit to relay M and shortcircuits relay G G releases. Relay B releases, opens the holdingcircuits to relays H and K prepares a circuit to relay D removes amultiple ground from the P lead, opens the circuit to relay C and opensthe short across the winding of relay G Relay G reoperates, closes acircuit to relay D until relay K releases and opens its circuit at K 5.Relay G restores, closes a circuit to relay C which closes a circuit torelay M Relay M in turn grounds the P lead to maintain the circuit busy.Relay G also opens the circuit to relay D which releases after a relaydue to its slow release characteristics and opens the circuit to relay CRelay C restores, opens the circuit to relay M Relay M releases andremoves ground from the P lead making the circuit available for othercalls. The repeater in the distant office is released after relay Kremoves battery from the DL lead, and has the release time of relays D Cand M in which to restore.

Referring to Fig. 5, if a local subscriber in the Tandem Office dials asecond digit (-for example corresponding to the level of the groupselector, 181 in the Tributory Ofiice which is assigned for toll accessonly, theincoming selector 181 -will he stepped to its tenth level inwhich it hunts for an idle Verification Distributor VD, the detailedcircuit of which is shown in Fig. 4 to which reference should now bemade.

An absence of ground on the P lead makes this switch idle to huntingincoming selectors.

When a selector stops on the terminals assigned to the switch, itconnects ground to the P lead to make it busy to other hunting selectorsand connects a loop to the and leads in known manner. Relay A operatesvia the loop and at A 1 closes a circuit to relay B Relay B operates, atB 1 prepares an impulsing circuit to the minor switch magnet OM and the12 Winding of relay 0* in parallel and opens part of the circuit to therelease magnet ZM, at B 3 closes a circuit to the preenergiz ing winding(3-4) of relay C via the minor switch off normal springs CMI, at B 2prepares a circuit for the operation of relay D and at B 4 closes acircuit to relay F Relay C operates, opening at C 1 part of a circuit torelay D The remaining contacts of relay C are not efiective at thistime.

7 Relay F operates slowly due to the copper slug on its core. Relay Fwhen operated, at F 1 and F 2 restores the polarity of the loop tonormal. A reverse battery preliminary supervisory signal, therefore, issent to the preceding equipment until relay F operates.

In the repeater, Fig. 1, upon the reversal of battery over the SW and|SW leads, relay F will operate over winding 12 and rectifier MRAZ and,in turn, will operate relay A. Relay A replaces ground on the DL leadwith resistance battery to repeat the signal to the Tandem Office. Atthe same time, a circuit will be closed over F2 to relay H. Relay H willnot operate immediately due to the long delay provided by the thermistorTH. When the reverse battery signal is removed in approximatelymilliseconds, relay F releases and, in turn, releases relay A. Relay Aremoves the signal from the distant equipment and prepares for the nextdigit. Relay F, on release, opens the circuit to relay H. Relay D isheld during this interval via the rectifier MRB, and contacts U6, B4 andH3.

In the Tandem Office repeater, Fig. 2, the replacement of ground bybattery over the DL2 lead causes relay G to release. Relay G closes acircuit to relay R during the release time of relay M via G 1, F 2, C 1,M 1, K 2. Relay M is operated by the relay C during dialing and releasesafter the release of C after each digit. Relay M is slow to release toprovide an interval for the operation of relay R Relay R at R 1 removesa short circuit from the 1-2 winding of K Relay K operates in serieswith the cut through relays of the preceding switches. If, however, thecall had been originated by a toll operator, a forward ground on the Plead prevents the operation of relay K at this time. Relay K is slightlyslow to operate to prevent it from operating on any extraneous operationof relay R Relay K locks via its 34 winding to the ground provided byrelay B at B 1, at K 3 closes a locking circuit to relay R at K 4.connects direct ground on the P lead and opens the circuit to its 1-2winding, and at K 5 disables the pulsing contact A 1 in the pulsingcircuit to the DL lead. The relay A is now disabled and no furtherdigits can be sent to the distant oflice. The operation of relay R atthis time does not provide answer supervision (reversal of the linepolarity) to the called party due to the unoperated condition of relay HCall from toll operator to subscriber in T ributory Ofiice The call isextended over the two-way trunk Tru2, Fig. 5, and the repeater Rep3 toan idle incoming selector 183, which is stepped to its,fifth level inwhich it hunts for an idle auto-to-auto repeater RepZ. These operationsbeing accomplished as described in the preceding call. I

The. repeater RepZ of Fig. 2 is seized and repeats impulses to therepeater, Fig. l, at the Tributory Otfice, as described in connectionwith a call from a subscriber in the Tandem Ofiice to a subscriber inthe Tributory Office.

In the repeater of Fig. l at the Tributory Ofiice, the impulse repeatingand correcting relays L, T cause the setting of the succeeding localequipment and establish the connection to the. Wanted line as alreadydescribed, and the called party is rung in known manner. When the callis answered, reversal of battery over the +SW and SW leads causes groundon the lead D1. to be replaced by bat'tery resistance and the relay GFig. 2, in the Tandem Officerepeater operates and closes a circuit forrelay H over G 1, B 2, F 2, C 1, M 1. Relay H locks to ground at B lland H 4 closes a circuit for relay R which at R 4 and R 8 reversesbattery over the +L and L leads to give answer supervision to theoperator. In this case, however, ground forwarded over the P lead fromselector 183 (Fig. prevents the operation of relay K and leaves relay Runder the control of relay G also the pulsing contacts A 1 are notshunted by contacts K 5.

If the toll operator disconnects first, the replacement of resistancebattery by ground on the lead DL at the repeater of Fig. 3 releasesrelay H which opens the circuit to relay (3 and the circuit functions asalready described in connection with the preceding call. Relay G opensthe loop circuit to the incoming local selector (183, Fig. 5) causingthe release of relay A in the repeater of Fig. 2 to which referenceshould now be made.

The release of relay A releases relay F and replaces resistance batterywith ground on the DL and +L and -L leads of the trunk (simplex) overthe winding of relay G thus giving distant disconnect supervision andreoperating relay G Relay F opens the circuit of relay R at P 4 (make)but an alternate circuit to relay R is closed over G 1, B 2, F 2(break), H 4 and K 2. Relay R maintains relay B? operated. If R releasesmomentarily during the transfer time of its holding circuit, B remainsoperated since it is slow to release. When the distant equipment isreleased, G releases and, in turn, releases-R B and H Relay C operatesduring the release of B and closes a circuit to M M places a ground onthe P lead to maintain the repeater busy until all relays are released.Relay M removes ground from the P lead, allowing the preceding switchesto release, and this circuit is ready for the next call.

In the repeater, Fig. 1, at the Tributory Ofiice, the replacement ofresistance battery with ground over the +L and -L lead of the trunk andthe lead DL operates relay G which releases relay S, causing the releasein turn of relays D, U and A. Relay U opens the loop to the succeedingequipment and relay F restores and in turn releases relays B and H.Relay A replaces resistance battery with ground to the winding of relayG, which releases. The circuit is now ready for the next call.

If the called party at the Tributory Office disconnects first, asucceeding switch reverses battery over the leads +SW and SW causingrelay F to restore. Relay F opens the circuit to relay S and a multiplecircuit to relay B, prepares an alternate circuit to relay S andreleases relay A. Relay A replaces resistance battery with ground to thewinding of relay G thus giving the operator disconnect supervision.Relay G also recloses the circuit to relay S.

In the repeater at the Tributory Ofiice, Fig. 2, relay G operates andreleases relay R which reverses battery towards the operator in order togive disconnect supervision, and closes part of the circuit of relay CThe battery reversal causes relay E Fig. 3, in the auto-to-auto manualrepeater to restore and this circuit functions in the manner describedin connection with a call from the toll operator to a subscriber in theTandem Office.

When the operator disconnects, the replacement of resistance batterywith ground on the lead DL opens the circuit to relay H which restoresand deenergizes relay G Relay G opens the loop circuit to the succeedinglocal incoming selector causing it to restore.

In the repeater, Fig. 2, relay A is released and, in turn releases relayF Relay A replaces resistance battery with resistance ground on the leadDL and on the +L and L leads of the trunk (simplex) over the winding ofrelay G thus allowing the succeeding equipment to release and releasingG Relays B and H restore. Relay C operates during the release time ofrelay B and 14 operates relay M Relay M grounds the P lead to maintainthe circuit busy' to provide time for the succeeding equipment torelease. Relay C releases and releases M Relay M removes ground from theP lead, allowing the preceding switches to restore, and this circuit isready for the next call.

In' the repeater, Fig. 1, at the Tributory Ofiice the replacement ofbattery resistance with ground over the lead DL causes the release ofrelay G and in turn relays S, B, D, U'and H are released.

Verification call from toll operator to subscriber in Tributary OfiiceThe call is extended to the incoming selector 181, Fig. 5, under thecontrol of the toll operator as described in connection with a call fromthe toll operator to a Tributory' Ofiice subscriber. The operator thendials the thousands digit 0 to seize and idle Verification Distributor,Fig. 4, which sends a preliminary reverse battery signal lasting aboutmilliseconds to the preceding equipment as already described.

In the repeatenFig. 1, upon the reversal of battery over the SW and +SWleads relay F will operate and, in turn, operate relay A. Relay Areplaces ground on the lead DL with resistance battery to repeat thesignal to the Tandem Oflice. At the same time, a circuit will be closedover F2 to relay H. H will not operate during the preliminary reversebattery signal due to the long delay provided by the thermistor TH. Whenthe reverse battery signal is removed in approximately 100 milliseconds,relay F releases and, in turn, releases relay A. Relay A removes thesignal from the distant equipment and prepares for the next digit. RelayF, on release, opens the circuit to relay H. Relay D is held during thisinterval via the rectifier MRB, and contacts H3, B4, U6. When a selectorstops on the terminals assigned to the verification distributor, Fig. 4,relay A operates over the incoming loop and energizes relay B whichprepares the impulsing circuit to the stepping magnet OM of the minorswitch MS and the winding of relay C in parallel.

The circuit is -now prepared to receive further dial impulses. Relay Areleases for each dial impulse received, opening the circuit to relay Band closing the circuit to the minor switch magnet OM and relay Cwinding (1-2) in parallel. The minor switch wipers are driven to thefirst terminal of the bank as OM is energized, thus operating its offnormal springs CM. The CM springs open the circuit to the pre-energizingwinding of relay C and close part of the circuit to release magnet ZM.Relay B is slow to release and remains operating during impulsing. RelayC 'remains operated via its 12 winding.

Relay A reoperates on the next loop closure, closing the circuit torelay B releasing the minor switch magnet OM, and opening the circuit torelay C Relay C is slow to release and remains operated duringimpulsing. The above cycle of the release of relay A and the operationof magnet OM and the holding of relay C is repeated until the completedigit is received positioning the minor switch Wipers on the dialedterminal. When relay A remains operated at the end of the digit, relay Creleases closing a circuit to relay D Relay D operates, transferring theand f+ leads from the windings of relay A to the M81 and MSZ wipersrespectively and extending the loop connection to a verificationconnector CONZ, Fig. 5, having access to the wanted line.

The circuit is now held under control of a ground for- Warded over the Plead. Relay A releases after relay D operates, releasing relay B Thecircuit to the release magnet ZM is held open by a break contact D 4 ofrelay D The P lead is common to all the verification connectors (thislimits the verification trunk group to l) and is extended to the P leadof the calling line via the connector which responds to the tens andunits digits in known manner. If the called line is busy, relay Creoperates via its (34) winding from the ground on the calledsubscribers P lead. Relay when reoperated, reverses the polarity via itsC 2 and C 3 contacts to the preceding equipment prior to cut through tothe and leads of the called line thus providing a busy signal to theoperator without interference to the established connection.

If the line is idle, the operator does not receive answer supervisionand cannot signal the line as no ringing provisions are provided.

The circuit is released when the loop to the 1+ and leads is opened andthe ground is removed from the P lead consequent upon the operatordisconnecting. Relay D releases and closes a circuit to ZM and reclosesa ground to the P lead to maintain the switch busy until it completesits release. The circuit to the connector is opened when this circuitreleases, opening the circuit to the 3-4 winding of relay C it operated.

Call from subscriber in Tandem Ofiice to toll operator The call isextended over a subscribers line circuit LCZ, Fig. 5, line finder LFl,group selector 682 (10th level) repeater Rep3 and trunk Tru2 to the tolloperators position TB.

In this case the repeater Rep3, Fig. 3, is taken into use over the pathof access -L(1), -|-L(1) and operates in the same manner as previouslydescribed in connection with a call from the Tributory Oflice with theexception that the operation of relay M does not reverse the polarity ofthe line L(1) and +L(1), since it is not necessary to provide answersupervision on calls from the local ofiice.

Call from toll operator to subscriber in Tandem Ofiice When a call isinitiated by the operator over the two-way trunk TruZ, Fig. 5, batteryis applied over the trunk conductors to the lead DL Fig. 3.

Relay G operates, at G 1 closes the circuit to relay D and at G 2 closespart of the circuit for seizing the succeeding local equipment (e. g.the incoming selector 183, Fig. Relay D operators, at D 2 prepares thecircuit to relay C at D 4 places ground on the P sw lead to provide atoll marking to the succeeding local equipment and closes the circuit torelay L at D 1 removes the 600 ohms termination YD from the line, and atD 5 closes the circuit to the 12 winding of relay H Relay H operates andat H 1 prepares a local circuit for relay G Relay L operates, at L 1removes ground from the ATE lead to provide for metering an all trunksbusy condition and places ground on the P lead to make this circuit busyto outgoing calls, at L 2 and L 3 disconnects thewinding of relay A andcloses the circuit for seizing the succeeding local equipment over the+SW and SW leads over contacts L 5, G 2, L 4, L 2, L 3, and L 6 andthrough the series parallel combination of relay E and rectifiers MRA 1and MRA 2. The unidirectional characteristics of MRA 1 prevent .relay Efrom operating over the loop circuit to the succeeding equipment at thistime. The succeeding local equipment, on being seized, returns groundover the P sw lead, thus closing a parallel circuit to relay L RelayGtfollows the impulses received over the DL lead and when atnormal,opens the circuit to relay D closes the circuit to relay C and at G 2opens the loop circuit to the succeeding local equipment. Relay Coperates on the first impulse of each series and at C 1 shunts thewinding 34 of the repeating coil RC with resistance YB to improveimpulsing conditions.

After the last impulse of eachseries, relay G remains operated, openingthe circuit to relay C closing the circuit to relay D and closing theloop circuit to the succeeding local equipment. Relays C and D? are slow to release and remain operated during imp-ulsing. Relay C onrestoring after the last impulse of each series, re-

moves the shunt from winding 3-4 of repeating coil The succeeding localequipment follows the impulses received, establishes a connection to thedialed line and signals the dialed subscriber all in well-known manner.

When the call is answered, a succeeding local switch reverses batteryover the +SW and SW leads, causing relay E to operate.

Relay E on operating, at E1 closes the circuit to relay J and closes thecircuit to the 12 and 34 windings of H in series over contacts E 2, J 2,D 5 and protective resistor YA Relay J operates, at J 2 transfers thelead DL from ground through relay G to ground through the 12 and 34windings of relay H giving high-resistance answer supervision to thedistant office, at J 3 closes a local holding circuit to relay G andcloses over J 1, B 4 its own locking circuit. Relay H remains operatedover its 1-2 and 3-4 windings to battery over lead DL When the dialedparty disconnects first, a succeeding local switch reverses battery overthe +SW and SW leads causing relay E to restore.

Relay E upon restoring, removes "at E 1 a multiple ground from the Plead and replaces at E2 the ground to the. lead DL through the 1-2 and34 windings of H with ground through the 12 windings of H to givelowresistance disconnect supervision to the distant ofiice. 'Relay Hremains operated over its 1-2 winding from battery forwarded over thelead DL When the operator in the distant ofiice disconnects, theequipment in the distant office replaces resistance battery on the leadDL with ground, thus opening the circuit to the 12 winding of relay HRelay H restores and opens the circuit to relay G Relay G restores andat G 2 opens the loop circuit to the succeeding local equipment,allowing it to restore. Relay (It also at G 1 opens the circuit to relayD and closes the circuit to relay C Relay C operates and at C 2 preparesthe peg count metering circuit over wire PC. Relay D restores, at D 2opens the circuit to relay C and removes a multiple ground from the P swlead' at D 4. I

The succeeding local equipment removes ground from the P sw lead, thusopening the circuit to relay L Relay L restores, at L 1 places ground onthe ATE lead and on the PC lead to the peg cOunt before relay Crestores, and opens the circuit to relay J Relay C restores and opensthe circuit to the PC lead and relay J restores.

When the operator disconnects first, the equipment in the distant ofiicereplaces resistance battery on the lead DL with ground, thus opening thecircuit to relay H Relay H restores and at H 1 opens the circuit'torelay G Relay G restores and the circuit functions as already explainedin connection with release when the called party disconnects first.

While there has been shown and described the application of ourinvention to a single modification it will be understood that variousomissions and substitutions and changes in the details of the apparatusillustrated in its operation may be made by those skilled in the artwithout departing from the spirit of our invention. It is the intention,therefore, to be limited only by the scope of the following claims. g II What is claimed is: a a

1. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a second automatic exchange,a second impulse repeater in said second automatic exchange, a trunkline extending from said first impulse repeater to said second impulserepeater, an operators toll board, automatic switch means for extendinga connection from a subscriber in said second exchange-to a subscriberinsaid first exchange, automatic switch means in said first exchangespecially assigned for use only by the toll operator, means forextending a connection from said toll board over said secnd repeater,said trunk line, said first repeater and said specially assigned switchmeans, means for transmitting a signal from said toll board to saidsecond repeater when said last-mentioned connection is initiated, meansin said specially assigned switch means for sending a signal to saidsecond repeater during an interdigital period, means in said secondrepeater responsive to said signal from said specially assigned switchmeans for preventing the repetition of further impulses over said trunkline to said first repeater, and means in said second repeaterresponsive to said signal from said toll board for blocking theoperation of said impulse-preventing means.

2. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a second automatic exchange,a second impulse repeater in said second automatic exchange, a trunkline extending from said first impulse repeater to said second impulserepeater, an operators toll board, automatic switch means for extendinga connection from a subscriber in said second exchange to a subscriberin said first exchange, automatic switch means in said first exchangespecially assigned for use only by the toll operator, a line comprisinga pair of talking conductors extending from said first repeater and overwhich access is had to said specially assigned switch means, means forextending a connection from said toll board over said second repeater,said trunk line, said first repeater and said pair of talking conductorsto said specially assigned switch means, means for transmitting a signalfrom said toll board to said second repeater when said connection isinitiated, means in said specially assigned switch means for sending areverse battery signal over said pair of talking conductors to cause thesending of a signal to said second repeater during an interdigitalperiod, means in said second repeater responsive to said signal forpreventing the repetition of further impulses over said trunk line tosaid first repeater, and means in said second repeater responsive tosaid signal from said toll board for blocking the operation of saidimpulse-preventing means.

3. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a second automatic exchange,a second impulse repeater in said second automatic exchange, a trunkline extending from said first impulse repeater to said second impulserepeater, an operators toll board, automatic switch means for extendinga connection from a subscriber in said second exchange to a subscriberin said first exchange, automatic switch means in said first exchangespecially assigned for use only by the toll operator, a line comprisinga pair of talking conductors extending from said first repeater and overwhich access is bad to said specially assigned switch means, means forextending a connection from said toll board over said second repeater,said trunk line, said first repeater and said pair of talking conductorsto said specially assigned switch means, means for transmitting a signalfrom said toll board to said second repeater when said connection isinitiated, means in said specially assigned switch means for sending arevesse battery preliminary answer signal over said pair of talkingconductors to said first repeater during an interdigital period, meansin said first repeater responsive to said battery reversal for sending asignal over the two conductors of said trunk line in simplex, means insaid second repeater responsive to said 'last-mentioned' signal forpreventing the repetition of further impulses over said trunk line tosaid first repeater, and means in said second repeater responsive tosaid signal from said toll board for blocking the operation of saidimpulsepreventing means.

4. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a tandem automatic exchange,a second impulse repeater in said tandem automatic exchange, a firsttrunk line extending between said first and second repeaters, a thirdimpulse repeater at said tandem automatic exchange, an

operators toll board, a second trunk line extending from said thirdrepeater to said toll board, switch means for extending a connectionfrom a subscriber in said tandem exchange to a subscriber in said firstautomatic exchange over said second and first repeaters and said firsttrunk 'line, switch means in said first automatic exchange speciallyassigned for use only by the toll operator, means for extending aconnection from said operators toll board to a subscriber in said firstautomatic exchange over said third, second and first repeaters, saidsecond and first trunk lines and said specially assigned switch means,mean-s for transmitting a signal from said toll board over said secondtrunk line and said third repeater to said second repeater when saidlast-mentioned connection is initiated, means in said specially assignedswitch means for sending a signal to said second repeater during aninterdigital period, means in said second repeater responsive to saidlast-mentioned signal for preventing the repetition of further impulses,and means in said second repeater responsive to said signal from saidtoll board for blocking the operation of said impulse-preventing means.

5. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a tandem automatic exchange,a second impulse repeater in said tandem automatic exchange, a firsttrunk line extending between said first and second repeaters, a thirdimpulse repeater at said tandem automatic exchange, an operators tollboard, asecond trunk line extending from said third repeater to saidtoll board, switch means for extending a connection from a subscriber insaid tandem exchange to a subscriber in said first automatic exchangeover said second and first repeaters and said first trunk line, switchmeans in said first automatic exchange specially assigned for use onlyby the toll operator, means for extending a connection from saidoperators toll board to a subscriber in said first automatic exchangeover said third, second and first repeaters, said second and first trunklines and said specially assigned switch means, means for transmitting asignal from said toll board to said second repeater over said secondtrunk line and said third repeater when said last-mentioned connectionis initiated, means in said specially assigned switch means for sendinga signal to said second repeater during an interdigital period, impulserepeating contacts in said second repeater, means in said secondrepeater for testing for the presence or absence of said signal duringsaid interdigital period, means responsive to said signal for renderingsaid impulse repeating contacts ineffective, and means in said secondrepeater responsive to said signal from the toll board for blocking theoperation of said means for rendering said impulserepeater contactsineffective.

6. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a tandem automatic exchange,a second impulse repeater in said tandem automatic exchange, a firsttrunk line extending between said first and second repeaters, a thirdimpulse repeater at said tandem automatic exchange, an operators tollboard, a second trunk line extending from said third repeater to saidtoll board, switch means for extending a connection from a subscriber insaid tandem exchange to a subscriber in said first automatic exchangeover said second and first repeaters and said first trunk line, averification distributor switch in said first automatic exchangespecially assigned for use only by the toll operator, means forextending a connection from said operators tol'l board to a subscriberin said first automatic exchange over said third, second and firstrepeaters, said second and first trunk lines and said verificationdistributor switch, means for transmitting a signal from said toll boardto said second repeater over said second trunk line and said thirdrepeater when said last-mentioned connection is initiated, means in saidverification distributor switch for sending a signal to said ime secondrepeater during an interdigital period, impulse repeating contacts insaid second repeater, means in said second repeater for testing for thepresence or absence of said last-mentioned signal during saidinterdigital period, means responsive to said last-mentioned signal forrendering said impulse repeating contacts ineffective, and meansresponsive to said toll board signal for blocking the operation of saidmeans for rendering said impulserepeater contacts ineffective.

7. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a tandem automatic exchange,a second impulse repeater in said tandem automatic exchange, a firsttwo-way trunk line extending between said first and second repeaters, athird impulse repeater at said tandem automatic exchange, an operatorstoll board, avsecond two-way trunk line extending from said thirdrepeater to said toll board, switchmeans for extending a connection froma subscriber in said tandem exchange to a subscriber in said firstautomatic exchange over said second and first repeaters and said firsttrunk line, switch means in said first automatic exchange speciallyassigned for use only by the toll operator, means for extending aconnection from said operators toll board to a subscriber in said firstautomatic exchange over said third, second and first repeaters, saidsecond and first trunk lines and said specially assigned switch means,means for transmitting a signal from said toll board to said secondrepeater over said second trunk line and said third repeater when saidlast-mentioned connection is initiated, means in said specially assignedswitch means for sending a signal to said second repeater during aninterdigital period, means in said second repeater responsive to saidlast-mentioned signal for preventing the repetition of further impulses,and means responsive to said toll board signal for blocking theoperation of said means for preventing the repetition of further pulses.

8. In a telephone system, a first automatic exchange, a first impulserepeater in said first automatic exchange, a second automatic exchange,a second impulse repeater in said second automatic exchange comprising apair of impulse repeating contacts, a trunk line extending from saidfirst impulse repeater to said second impulse repeater, an operatorstoll board, automatic switch means for extending a connection from asubscriber in said second exchange to a subscriber in said firstexchange, automatic switch means in said first exchange speciallyassigned for use only by the toll operator, a line comprising a pair oftalking conductors extending from said first repeater and over whichaccess is had to said specially assigned switch means, means forextending a connection from said toll board over said second repeater,said trunk line, said first repeater and said pair of talking conductorsto said specially assigned switch means, I

20 said toll board and from a local substation in said second automaticexchange, means for rendering saidimpulserepeating contacts ineffective,and means forcontrolling said last-mentioned means jointlydependent uponthe operation of said testing means and said discriminating means.

9. In a telephone system, the combination according to claim 8 in whichsaid second impulse repeater comprises a first slow release relay, meansfor energizing said relay during the transmission of impulses anddeenergizing said relay during interdigital periods, the meansresponsive to saidsignal sent over the two conductors of said trunk linein simplex, comprising a second relay, 8. third relay, and a circuit forsaid third relay including front contacts of said first relay and backcontacts of said second relay, the means for controlling theinelfectiveness of the impulse-repeating contact-s comprising a fourthrelay having a Winding normally connected to a private wire, a shortcircuit for said winding including back contacts of said third relay,and front contacts on said fourth relay for shunting said impulserepeating contacts.

10. In a telephone system, the combination according to claim 8 in whichsaid first impulse repeater comprises a pair of impulse repeatingcontacts, a first relay responsive to reverse battery signals, a secondrelay having normally connected in its circuit a thermistor and backcontacts of said first relay, a third relay adapted to be operated whensaid first repeater is seized over said first trunk line, a shortcircuit for said thermistor including back contacts of said third relay,and means under the control of said second relay for rendering saidimpulse repeating contacts ineffective, said thermistor having suchcharacteristics that said second relay does not operate during theduration of said preliminary answer signal.

11. In a telephone system, a first automatic exchange, a firstimpulse-repeater in said first automatic exchange, a second automaticexchange, a second impulse repeater in said second automatic exchange,atrunk line extending from said first impulse-repeater to said secondimpulserepeater, an operators toll board, means for connecting said tollboard to said second repeater, automatic switch means for extending aconnection from a subscriber in said first exchange either to asubscriber in said second exchange or to said toll board, first andsecond paths of access over which said first impulse repeater may beseized by a calling party in said first exchange, and means in saidfirst repeater responsive to its seizure over one of said paths ofaccess for automatically transmitting a predetermined number of impulsesover said trunk line to route the call to said operators toll board,said first impulse-repeater comprising a pulsing circuit fortransmitting impulses over said trunk 'line, a first slow-release relay,a second relay connected only to one of said paths of access, a circuitfor said first relay including back contacts of said second relay, meansfor energization of said second relay responsive to the seizure of saidrepeater over said last-mentioned path of access, and means for openingsaid pulsing circuit during the energization of the second relay and therelapse of the first relay.

References Cited in the file of this patent UNITED STATES PATENTS

